Refined cast steel and preparation method

Abstract

The invention relates to the technical field of refined steel materials, in particular to refined cast steel and a preparation method thereof.The refined cast steel comprises, by mass, 800 parts of waste steel with the C content being 0.1%, 200 parts of pig iron with the C content being 3.5%, 18.5 parts of ferromanganese, 24 parts of ferrochromium, 5 parts of metallic nickel, 3 parts of ferromolybdenum, 0.2 part of ferrovanadium, 0.02 part of ferroboron and 11.5 parts of deoxidizer; wherein the deoxidizing agent comprises 10 parts of silicon iron for pre-deoxidization and 1.5 parts of aluminum for final deoxidization; the prepared refined cast steel comprises 0.25% of C, 1.7% of Mn, 2.3% of Cr, 0.5% of Ni, 0.3% of Mo, 0.09% of V, 0.0035% of B and the balance of Fe, the refined cast steel is subjected to dephosphorization and desulfurization treatment through slagging-off and slagging, meanwhile, an argon blowing step in the pouring process is matched, primary treatment is rapidly achieved through argon blowing treatment and the reactivity of active gas, then the inert and stirring capacity of argon is utilized, and the molten steel is subjected to continuous casting. And early-stage side effects are eliminated, deep refining is achieved, and effective control over P and S elements in refined cast steel is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of fine steel materials, and specifically provides a refined cast steel and a preparation method thereof. Background Art

[0002] Refined cast steel refers to a type of engineering material obtained by optimizing cast steel (steel produced by casting) through specific refining processes to improve its purity, compositional uniformity, and mechanical properties.

[0003] Cast steel is based on iron, with a carbon content usually between 0.1% - 0.6% (different from cast iron), and is a type of steel directly made into part blanks through melting and casting (such as sand casting, investment casting, etc.). Its advantage is that it can form complex structures, but its disadvantages are that it may have problems such as porosity, shrinkage porosity, and compositional segregation.

[0004] During the steelmaking or casting process, through external refining technologies (such as LF furnace refining, VD vacuum degassing, VOD vacuum oxygen decarburization, etc.) or post-casting heat treatment, impurities in the molten steel (such as sulfur, phosphorus, gases [H / N / O], inclusions) are removed, alloying elements are adjusted, and the tissue uniformity is improved, thereby enhancing the performance.

[0005] However, currently, refined cast steel has the problem of excessive S / P or high P content. The main reason for this problem is that during the process of refining cast steel, the oxidation of P and S elements is insufficient.

[0006] For example, in the invention patent with the patent application number 202411220974.0, a multifunctional refining device for cast steel is specifically disclosed. Through the setting of the dephosphorization device, the injection of oxygen increases the oxygen activity in the molten steel, improves the oxidation rate of phosphorus elements in the molten steel, and helps to more effectively separate the phosphorus-containing slag from the molten steel.

[0007] Therefore, during the process of refining cast steel, it is necessary to effectively control the oxidation sufficiency of P and S elements. Summary of the Invention

[0008] In view of the above problems, the present invention provides a refined cast steel and a preparation method thereof. Through slag skimming and slag making, the refined cast steel is subjected to dephosphorization and desulfurization treatment. At the same time, in cooperation with the argon blowing step during pouring, by means of argon blowing treatment, nitrogen, carbon monoxide, water vapor, and air are injected into the molten steel, and then argon is blown in. The reactivity of the active gases is used to quickly achieve preliminary treatment, and then the inertness and stirring ability of argon are utilized to eliminate the side effects in the early stage and achieve deep refining, so as to effectively control the P and S elements inside the refined cast steel.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A refined cast steel, comprising the following raw materials by mass ratio:

[0011] 800 parts of scrap steel with a C content of 0.1%, 200 parts of pig iron with a C content of 3.5%, 18.5 parts of ferromanganese, 24 parts of ferrochrome, 5 parts of metallic nickel, 3 parts of ferromolybdenum, 0.2 parts of ferrovanadium, 0.02 parts of ferroboron, and 11.5 parts of deoxidizer;

[0012] Among them, the deoxidizer includes 10 parts of ferrosilicon for preliminary deoxidation and 1.5 parts of aluminum for final deoxidation;

[0013] The prepared refined cast steel contains 0.25% C, 1.7% Mn, 2.3% Cr, 0.5% Ni, 0.3% Mo, 0.09% V, 0.0035% B, and the rest is Fe.

[0014] In addition, the method for preparing the above-mentioned refined cast steel according to the present invention includes the following steps:

[0015] Step a: Charging. Lay 10 parts of ferrosilicon and 5 parts of ferromanganese at the bottom of the electric arc furnace, load 800 parts of scrap steel and 200 parts of pig iron on the upper layer, and load 5 parts of alloy nickel plate with the scrap steel;

[0016] Step b: Skimming and slag making. After melting, skim the initial slag, add 50 parts of lime and 10 parts of fluorite as slag-making materials, heat up to 1620 °C, hold for 10 min, and dephosphorize and desulfurize until S ≤ 0.02% and P ≤ 0.025%;

[0017] Step c: Alloying. At 1620 °C, add 24 parts of ferrochrome and 3 parts of ferromolybdenum, stir and keep warm for 15 min to ensure complete dissolution. At 1600 °C, add the remaining 13.5 parts of ferromanganese, stir for 5 min. 10 min before tapping, at 1580 °C, first add 0.1 part of ferrovanadium, stir for 3 min, add 1.5 parts of aluminum ingot, add 0.02 parts of ferroboron, and the remaining 0.09 parts of ferrovanadium, stir quickly for 2 min to avoid boron oxidation and burning loss, send electricity to melt, gradually increase the power to 400 kW, control the melting period temperature at 1550 - 1600 °C, and the melting time is 60 - 70 min;

[0018] Step d: Composition adjustment. Take samples for spectral analysis. If the C content is insufficient, add carbon powder with ≤ 0.1%; if the S / P exceeds the standard, add lime and fluorite for slag-making treatment;

[0019] Step e: Casting. At 1520 - 1540 °C, pour the molten steel into the resin sand mold, with a pouring speed of 5 - 15 kg / s, keep the pouring cup in a full-flow state, and 4 - 6 h after pouring, the sand mold temperature drops to ≤ 200 °C,

[0020] Step f: Heat treatment. Immediately transfer to an annealing furnace for annealing, normalizing, and annealing treatments after opening the box.

[0021] As an improvement, in step f, the preliminary annealing is heated to 500 °C at a rate of 50 °C / h, held for 2 h, and then cooled to room temperature in the furnace to eliminate the casting stress. For the normalizing treatment, the heating temperature is 920 ± 10 °C, the holding time is calculated at 1 mm / min according to the thickness of the workpiece, the wind speed is 5 - 10 m / s, and it is cooled evenly. For the tempering treatment, the heating temperature is 620 ± 10 °C, the target hardness is HB220 - 250, the holding time is the same as that of the normalizing treatment, and it is heated in the furnace and then air-cooled to room temperature after holding.

[0022] As an improvement, in step e, during casting, the preheating temperature of the resin sand mold is 150 - 200 °C.

[0023] As an improvement, in step e, before casting, the ladle for containing molten steel is heated and baked through a ladle baking device.

[0024] As an improvement, the ladle baking device includes a bracket, a rotating arm, an upper cover plate, a hoist and a baking mechanism;

[0025] The bracket is fixedly arranged, the rotating arm is rotatably and swingably installed on the bracket, the upper cover plate is installed at the rotatably and swingably end of the rotating arm, and the baking mechanism is installed on the upper cover plate. The baking mechanism includes a combustion unit and an auxiliary combustion unit.

[0026] As an improvement, the combustion unit includes a gas pipe, a gas valve, a flame nozzle and a metal hose;

[0027] The gas pipe is communicated with an external gas supply device, the gas valve is arranged on the gas pipe to control the opening amplitude of the gas pipe, the flame nozzle is installed at the center position of the upper cover plate, and the flame nozzle is connected to the gas pipe through a metal hose.

[0028] As an improvement, the flame nozzle internally is provided with a cone arranged with lifting adjustment and spoiler rods arranged in a circular ring along the inner diameter of the flame nozzle and staggered.

[0029] As an improvement, the auxiliary combustion unit includes an auxiliary gas pipe, a butterfly valve, a fan and a flexible connecting pipe;

[0030] The auxiliary gas pipe is communicated with an external gas supply device, the butterfly valve is installed on the auxiliary gas pipe to control the opening amplitude of the auxiliary gas pipe, and the auxiliary gas pipe is connected to the flame nozzle through a hose, and the connection part is between the cone and the spoiler rods.

[0031] As an improvement, an argon blowing mechanism is also installed on the upper cover plate. The argon blowing mechanism includes an air inlet pipe, a telescopic pipe and a telescopic rod;

[0032] The intake pipe is connected to an external gas supply device, and the other end of the intake pipe is connected to a gas distribution area arranged inside the upper cover plate. The telescopic pipe is arranged below the upper cover plate, and the telescopic pipe is connected to the gas distribution area. The telescopic pipe is driven by a telescopic rod installed on the upper cover plate to perform telescopic movement.

[0033] The beneficial effects of the present invention are as follows:

[0034] In the present invention, phosphorus and sulfur removal treatment of refined cast steel is carried out through slag skimming and slag making. At the same time, in cooperation with the argon blowing step during the pouring process, by means of argon blowing treatment, nitrogen, carbon monoxide, water vapor, and air are injected into the molten steel, and then argon is blown in. The reactivity of the active gases is utilized to quickly achieve preliminary treatment, and then the inertness and stirring ability of argon are utilized to eliminate the side effects in the early stage and achieve deep refining, so as to effectively control the P and S elements inside the refined cast steel.

[0035] In the present invention, through "react first and then purify", while ensuring the treatment effect, the cost is reduced (such as using cheap N2 for pretreatment and then using Ar for refining). It is especially suitable for steel grades with strict restrictions on gas impurities (N, O) but requiring efficient reactions in the early stage (such as stainless steel decarburization and low-nitrogen steel refining).

[0036] In the present invention, an argon blowing mechanism is compounded on the ladle baking equipment. The argon blowing mechanism is used to carry out secondary refining treatment on the molten steel in the ladle, making the structure more concise. At the same time, when baking the ladle, the argon blowing mechanism can be used as a water vapor discharge device, and when carrying out argon blowing treatment, the auxiliary air pipe of the ladle baking equipment can be used as the discharge channel for gas impurities during argon blowing treatment, complementing each other and promoting each other.

[0037] In summary, the present invention has the advantages of high quality of refined cast iron, few impurities, and few internal defects in cast steel, etc. It is especially suitable for the technical field of refined cast steel materials and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic flow chart of the method in Embodiment 1 of the present invention;

[0039] Figure 2 It is a schematic three-dimensional structure diagram of the device in Embodiment 2 of the present invention;

[0040] Figure 3 It is a schematic three-dimensional structure diagram of the ladle in Embodiment 2 of the present invention;

[0041] Figure 4 It is a schematic three-dimensional structure diagram of the ladle baking mechanism in Embodiment 2 of the present invention Figure 1 ;

[0042] Figure 5 It is a schematic three-dimensional structure diagram of the ladle baking mechanism in Embodiment 2 of the present invention Figure 2 ;

[0043] Figure 6 It is a top - view structural schematic diagram of the bread - baking mechanism in Embodiment 2 of the present invention;

[0044] Figure 7 It is a sectional - view structural schematic diagram of the flame nozzle in Embodiment 2 of the present invention;

[0045] Figure 8 It is a schematic diagram of the extended state of the telescopic pipe in Embodiment 2 of the present invention;

[0046] Figure 9 It is a schematic diagram of the retracted state of the telescopic pipe in Embodiment 2 of the present invention;

[0047] Figure 10 It is a three - dimensional structural schematic diagram of the telescopic rod in Embodiment 2 of the present invention.

[0048] Marks in the drawings: Bracket 1, Rotary arm 2, Upper cover plate 3, Winch 4, Bread - baking mechanism 5, Combustion unit 51, Gas pipe 511, Gas valve 512, Flame nozzle 513, Metal hose 514, Cone 515, Turbulence rod 516, Auxiliary combustion unit 52, Auxiliary gas pipe 521, Butterfly valve 522, Fan 523, Flexible connection pipe 524, Argon - blowing mechanism 6, Inlet pipe 61, Telescopic pipe 62, Telescopic rod 63, Ladle 8, Turntable assembly 81, Rotary table 811, Swing arm 812, Hydraulic drive 813. Detailed implementation manners

[0049] The endpoints and any values disclosed in this article for ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0050] The following will elaborate on the specific implementation manners of the present invention. However, it should be noted that the protection scope of the present invention is not limited by these specific implementation manners, but is determined by the appended claims.

[0051] All publications, patent applications, patents, and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0052] When this specification uses prefixes such as "well-known to those skilled in the art", "prior art", or similar terms to introduce materials, substances, methods, steps, devices, or components, etc., the objects introduced by these prefixes cover those commonly used in the art at the time when the present invention is proposed, but also include those that are not commonly used at present but will become recognized in the art as suitable for similar purposes.

[0053] It should be particularly noted that two or more aspects (or embodiments) disclosed in the context of this specification can be combined with each other arbitrarily, and the technical solutions (such as methods or systems) formed thereby belong to a part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0054] Unless otherwise clearly specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless it does not conform to the common understanding of those skilled in the art when based on weight.

[0055] Example 1:

[0056] As Figure 1 shown, a refined cast steel includes the following raw materials by mass ratio:

[0057] 800 parts of scrap steel with a C content of 0.1%, 200 parts of pig iron with a C content of 3.5%, 18.5 parts of ferromanganese, 24 parts of ferrochrome, 5 parts of metallic nickel, 3 parts of ferromolybdenum, 0.2 parts of ferrovanadium, 0.02 parts of ferroboron, and 11.5 parts of deoxidizer;

[0058] Among them, the deoxidizer includes 10 parts of ferrosilicon for pre-deoxidation and 1.5 parts of aluminum for final deoxidation;

[0059] The prepared refined cast steel contains 0.25% of C, 1.7% of Mn, 2.3% of Cr, 0.5% of Ni, 0.3% of Mo, 0.09% of V, 0.0035% of B, and the rest is Fe.

[0060] The method for preparing the above-mentioned refined cast steel in this application includes the following steps:

[0061] Step a, charging: Lay 10 parts of ferrosilicon and 5 parts of ferromanganese at the bottom of the electric arc furnace, load 800 parts of scrap steel and 200 parts of pig iron on the upper layer, and load 5 parts of alloy nickel plate with the scrap steel;

[0062] Step b, slag skimming and slag making: After melting, skim the initial slag, add 50 parts of lime and 10 parts of fluorite as slag-making materials, heat up to 1620 °C, hold for 10 min, and dephosphorize and desulfurize until S ≤ 0.02% and P ≤ 0.025%;

[0063] Step c: Alloying. At 1620 °C, add 24 parts of ferrochrome and 3 parts of ferromolybdenum, stir and keep warm for 15 min to ensure complete dissolution. At 1600 °C, add the remaining 13.5 parts of ferromanganese, stir for 5 min. 10 min before tapping, at 1580 °C, first add 0.1 part of ferrovanadium, stir for 3 min, add 1.5 parts of aluminum ingot, add 0.02 part of ferroboron, and the remaining 0.09 part of ferrovanadium, stir rapidly for 2 min to avoid oxidation and loss of boron, then supply power to melt, gradually increase the power to 400 kW, control the temperature during the melting period at 1550 - 1600 °C, and the melting time is 60 - 70 min;

[0064] Step d: Composition adjustment. Take a sample for spectral analysis. If C is insufficient, add carbon powder with a content of ≤0.1%; if S / P exceeds the standard, add lime and fluorite to make slag for treatment;

[0065] Step e: Casting. At 1520 - 1540 °C, pour the molten steel into a resin sand mold, with a pouring speed of 5 - 15 kg / s, keep the pouring cup in a full-flow state. 4 - 6 h after pouring, the temperature of the sand mold drops to ≤200 °C,

[0066] Step f: Heat treatment. Immediately transfer to an annealing furnace after unpacking and perform annealing, normalizing, and annealing treatments in sequence.

[0067] Among them, in step f, for the preliminary annealing, heat up to 500 °C at a rate of 50 °C / h, keep warm for 2 h, and cool in the furnace to room temperature to eliminate the casting stress. For the normalizing treatment, the heating temperature is 920 ± 10 °C, and the holding time is calculated at 1 min / mm of the workpiece thickness, with a wind speed of 5 - 10 m / s for uniform cooling. For the tempering treatment, the heating temperature is 620 ± 10 °C, the target hardness is HB220 - 250, the holding time is the same as that of normalizing, heat up in the furnace, and after holding, air-cool to room temperature.

[0068] Further, in step e, during casting, the preheating temperature of the resin sand mold is 150 - 200 °C.

[0069] This application calculates the raw material addition amount in reverse according to the target composition (C 0.25%, Mn 1.7%, Cr 2.3%, etc.) and combines the burn-off rates of each element during melting (such as 8% burn-off of Mn and 5% burn-off of Cr). Using scrap steel and pig iron as the main raw materials, alloy ingots (Mn, Cr, Ni, Mo, etc.) and micro-alloying elements (V, B) are combined to ensure that the content of each element in the initial batching is slightly higher than the target value and just meets the standard after offsetting the burn-off.

[0070] Rapidly melt raw materials at high temperature (1600 °C) in an electric arc furnace to form uniform molten steel; after melting is complete, remove the initial slag (containing silicon and aluminum oxides and some sulfur and phosphorus impurities) to reduce the subsequent refining burden, and heat up to 1620 °C to make slag for dephosphorization and desulfurization: add lime (CaO, strongly alkaline) and fluorite (CaF2, flux) to form a high-alkalinity slag (CaO / SiO≈3 - 4), and hold at 1620 °C for 10 minutes to allow phosphorus (forming Ca(PO

[0071] )2) and sulfur (forming CaS) to fully enter the slag phase, with S≤0.02% and P≤0.025%, lower than the impurity standards of ordinary steel (usually S≤0.035% and P≤0.035%).

[0072] Furthermore, lay 10 kg of ferrosilicon (Fe - Si) at the bottom of the furnace. Utilize the reaction of Si with [O] in the molten steel to generate SiO2 (entering the slag) to reduce the initial oxygen content in the molten steel ([O]≤0.005%). Before tapping, add 1.5 kg of aluminum ingots (Al) in two batches. The reaction of Al with [O] generates high - melting - point AlO3 particles, which float to the slag layer. Finally, [O] in the molten steel is ≤0.002%, avoiding the crack risk caused by oxide inclusions.

[0073] In addition, add Ni (melting point 1455 °C), Mn (1246 °C), Cr (1857 °C, requires high - temperature dissolution), and Mo (2623 °C, added to the electric furnace in advance) in order of increasing melting point to ensure that the alloy is fully dissolved and the burn - off is stable.

[0074] If C is insufficient (e.g., the target is 0.25% and the actual measurement is 0.23%), add carbon powder (particle size ≤1 mm to avoid sulfur increase); if S / P exceeds the standard, add lime + fluorite to make slag for secondary removal to ensure that the composition fluctuation is ≤±0.02% (key elements).

[0075] Moreover, control the temperature of the molten steel at 1580 - 1590 °C (about 50 °C higher than the liquidus line) to avoid cold - lap defects caused by low - temperature casting; preheat the sand mold to 200 °C to reduce the casting stress. After heating to the austenite region, air - cool to transform coarse grains (such as as - cast dendrites) into fine - lamellar pearlite + ferrite, and the grain size can reach 8 - 9 grades (ASTM standard), with the strength increased by 15 - 20%. Eliminate the normalizing stress, make the carbides disperse, and increase the impact toughness by 30% to avoid brittle fracture.

[0076] In summary, compared with ordinary steelmaking (only one slag-making), this method reduces the S / P content to the national standard excellent level (S / P ≤ 0.030% for high-quality cast steel in GB / T 11352-2021) through a high-temperature and high-alkalinity slag system + two-stage deoxidation, significantly reducing the risks of hot brittleness (S) and cold brittleness (P), and improving the hot and cold processing performance of steel. The size of Al2O3 inclusions is ≤ 5μm, and the number is reduced by 60% compared with conventional deoxidation, avoiding excessive defects during flaw detection (such as ultrasonic testing).

[0077] By presetting the burning loss rate (such as Mn 8%, Cr 5%) and real-time spectral detection, the composition fluctuation range is controlled within ±0.015% (C), ±0.05% (Mn / Cr), far higher than the industry average level (usually ±0.05% / ±0.1%), ensuring stable performance of steel in different batches (tensile strength fluctuation ≤ 5 MPa).

[0078] V (0.09%) and B (0.0035%) are added in the form of master alloys (such as Fe-V, Fe-B), avoiding segregation caused by direct addition (B is easy to oxidize, V is easy to form carbides), ensuring their uniform distribution at grain boundaries, and exerting the best effects of refining grains (V) and improving hardenability (B).

[0079] Through the precipitation of carbonitriding of V (forming V(C,N) particles, size ≤ 10 nm), the growth of austenite grains is inhibited. After normalizing, the grain size is 2-3 grades finer than that of the steel without V, and the strength (σb ≥ 850 MPa) and toughness (Akv ≥ 40 J) are improved simultaneously.

[0080] Example 2:

[0081] As Figures 2 - 10 shown, this example provides a baking equipment for heating and baking the ladle used to hold molten steel before casting in Example 1.

[0082] Specifically, the baking equipment includes a bracket 1, a rotating arm 2, an upper cover plate 3, a winch 4, and a baking mechanism 5;

[0083] The bracket 1 is fixedly arranged, the rotating arm 2 is rotatably and swingably installed on the bracket 1, the upper cover plate 3 is installed at the rotatably and swingably end of the rotating arm 2, the winch 4 drives the rotating arm 2 to rotate and swing, and the baking mechanism 5 is installed on the upper cover plate 3. The baking mechanism 5 includes a combustion unit 51 and an auxiliary combustion unit 52.

[0084] After the upper cover plate 3 covers the opening at the top of the ladle, the combustion unit 51 and the auxiliary combustion unit 52 respectively discharge combustible gas and air or oxygen to heat the inside of the ladle, remove the water vapor inside the ladle, and simultaneously preheat the temperature of the ladle.

[0085] Among them, the combustion unit package 51 includes a gas pipe 511, a gas valve 512, a flame nozzle 513 and a metal hose 514;

[0086] The gas pipe 511 is connected to an external gas supply device. The gas valve 512 is arranged on the gas pipe 511 to control the opening and closing amplitude of the gas pipe 511. The flame nozzle 513 is installed at the center position of the upper cover plate 3, and the flame nozzle 513 is connected to the gas pipe 511 through the metal hose 514.

[0087] Moreover, a cone 515 with a lifting and adjusting setting is arranged inside the flame nozzle 513, and spoiler rods 516 are arranged in a circular ring along the inner diameter of the flame nozzle 513 and are staggered.

[0088] Furthermore, the auxiliary combustion unit 52 includes an auxiliary gas pipe 521, a butterfly valve 522, a fan 523 and a flexible connecting pipe 524;

[0089] The auxiliary gas pipe 521 is connected to an external gas supply device. The butterfly valve 522 is installed on the auxiliary gas pipe to control the opening and closing amplitude of the auxiliary gas pipe 521, and the auxiliary gas pipe 521 is connected to the flame nozzle 513 through the flexible pipe 524, and the connection part is located above the cone 515 and the spoiler rods 516.

[0090] In addition, an argon blowing mechanism 6 is also installed on the upper cover plate 3. The argon blowing mechanism 6 includes an air inlet pipe 61, a telescopic pipe 62 and a telescopic rod 63;

[0091] The air inlet pipe 61 is connected to an external gas supply device, and the other end of the air inlet pipe 61 is connected to a gas distribution area 31 arranged inside the upper cover plate 3. The telescopic pipe 62 is arranged below the upper cover plate 3, and the telescopic pipe 62 is connected to the gas distribution area 31, and the telescopic pipe 62 is driven by the telescopic rod 63 installed on the upper cover plate 3 to perform telescopic setting.

[0092] It should be noted that when the ladle is being baked, the gas pipe 511 transports combustible gas, such as coal gas, natural gas, etc., to the flame nozzle 513, while the auxiliary gas pipe 521 transports combustion-supporting gas, such as air or oxygen, etc., to the flame nozzle 513. The two gases converge at the flame nozzle 513, and after being mixed evenly, they are sprayed into the ladle interior to heat the ladle interior. At this time, the exhaust gas formed after combustion inside the ladle, such as water vapor, carbon dioxide, etc., is discharged outward through the telescopic pipe 62 in the argon blowing mechanism 6. At this time, the telescopic pipe 62 is in a contracted state driven by the telescopic rod 63 to avoid being damaged by the flame ejected from the flame nozzle 513.

[0093] After the ladle is completed with the baking treatment, the argon blowing mechanism 6 inputs gases into the ladle in the order of nitrogen, carbon monoxide, water vapor, air, and argon to treat the molten steel contained inside the ladle. The first stage: blowing in reactive gases (N2, CO, air, water vapor), using the reactivity of the reactive gases to quickly achieve preliminary treatment (such as decarburization, inclusion removal, composition adjustment), or reduce costs (N2 is cheaper than Ar). For example, for decarburization treatment: first blow in air / CO, and reduce the carbon content through oxidation reaction to quickly reach the target composition; for inclusion removal, blow in O2-containing gas to promote the aggregation and growth of inclusions (such as AlO3), or blow N2 to form bubble nuclei to increase the chance of inclusion collision and floating. In the second stage, switch to argon, and use the inertness and stirring ability of argon to eliminate the side effects in the early stage and achieve deep refining. For degassing and purification, when the argon bubbles float up, they adsorb gases such as H2 and N2 remaining in the early stage (especially the excessive N2 introduced by the reactive gas), further reducing the gas content; for inclusion removal, continuous stirring promotes the full floating of inclusions, and at the same time avoids introducing impurities by new reactive gases (such as preventing excessive nitrogen increase in the molten steel after stopping blowing N2); for uniform composition and temperature: argon stirring makes the composition and temperature of the molten steel more uniform, creating conditions for subsequent casting.

[0094] During this process, the auxiliary air pipe, in cooperation with the fan, discharges various impurity gases generated during the argon blowing treatment to the outside.

[0095] Furthermore, it should be noted that using the telescopic pipe 62 as the exhaust pipe of the argon blowing mechanism requires it to penetrate deep into the molten steel, and the upper cover plate 3 needs to seal the top opening of the ladle, which will cause interference between the exhaust pipe of the argon blowing mechanism with a fixed length and the opening of the ladle. Therefore, this application adopts a telescopic mechanism to avoid the interference problem and also avoid the problem of the telescopic pipe 62 being dried by the flame for a long time.

[0096] As a preferred implementation manner, the ladle 8 in this application adopts a rotating and switching double-headed ladle structure. When one group of ladles is undergoing the baking treatment, the other group of ladles is performing the casting work of molten steel. The cyclic switching of the two groups of ladles greatly improves the working efficiency. Specifically, the ladle 8 is provided with two groups that are driven by the turntable assembly 81 arranged below for rotating and switching. The turntable assembly 81 includes a set of rotating platforms 811, two sets of swing arms 812, and two sets of hydraulic drivers 813. The rotating platform 811 is driven to rotate by a motor in cooperation with an acceleration gear set, and the swing arms 812 are symmetrically installed on the rotating platform 811. The ladle 8 is placed on the corresponding swing arm 812, and the hydraulic driver 813 drives the corresponding swing arm 812 to swing, thereby driving the ladle 8 to tilt.

[0097] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A refined cast steel, characterized in that: The following raw materials are included by mass ratio: 800 parts of scrap steel with a C content of 0.1%, 200 parts of pig iron with a C content of 3.5%, 18.5 parts of ferromanganese, 24 parts of ferrochrome, 5 parts of metallic nickel, 3 parts of ferromolybdenum, 0.2 parts of ferrovanadium, 0.02 parts of ferroboron, and 11.5 parts of deoxidizer; The deoxidizer includes 10 parts of ferrosilicon for pre-deoxidation and 1.5 parts of aluminum for final deoxidation; The produced refined cast steel contained 0.25% of C, 1.7% of Mn, 2.3% of Cr, 0.5% of Ni, 0.3% of Mo, 0.09% of V, 0.0035% of B, and the remainder was Fe.

2. A method for preparing a refined cast steel according to claim 1, characterized in that: The following steps are involved: Step a, charging: 10 parts of ferrosilicon and 5 parts of ferromanganese are laid on the bottom of the electric arc furnace, 800 parts of scrap steel and 200 parts of pig iron are loaded on the upper layer, and 5 parts of alloy nickel plates are loaded with the scrap steel; Step b, slagging and slagging, after melting and clearing, remove the initial slag, add 50 parts of lime and 10 parts of fluorite as slagging materials, heat to 1620°C, keep for 10 minutes, dephosphorize and desulfurize to S≤0.02%, P≤0.025%; Step c, alloying, at 1620°C, add 24 parts of ferrochrome and 3 parts of ferromolybdenum, stir and keep warm for 15 minutes to ensure complete dissolution, add the remaining 13.5 parts of ferromanganese at 1600°C, stir for 5 minutes, 10 minutes before tapping, at 1580°C, first add 0.1 part of ferrovanadium, stir for 3 minutes, add 1.5 parts of aluminum ingot, add 0.02 parts of ferroboron, and the remaining 0.09 parts of ferrovanadium, stir quickly for 2 minutes to avoid boron oxidation and burning, send electricity for melting, the power is gradually increased to 400kW, the temperature during the melting period is controlled at 1550-1600°C, and the melting time is 60-70 minutes; Step d, composition adjustment, sampling spectral analysis, if C is insufficient, add ≤0.1% carbon powder; if S / P exceeds the standard, add lime and fluorite for slagging treatment; Step e: Casting: pour molten steel into the resin sand mold at 1520-1540°C at a pouring speed of 5-15kg / s. Keep the pouring cup full. 4-6 hours after pouring, reduce the sand mold temperature to ≤200°C. Step f, heat treatment, immediately transfer to the annealing furnace after unpacking for annealing, normalizing and annealing treatment in sequence.

3. The method according to claim 2, characterized in that: In step f, the preliminary annealing is carried out by heating the temperature to 500°C at 50°C / h, keeping the temperature for 2h, cooling to room temperature with the furnace to eliminate casting stress, the normalizing treatment is carried out at a heating temperature of 920±10°C, the holding time is calculated according to the workpiece thickness of 1mm / min, the wind speed is 5-10m / s, and the cooling is uniform. The tempering treatment is carried out at a heating temperature of 620±10°C, the target hardness is HB220-250, the holding time is the same as normalizing, the temperature is raised with the furnace, and the temperature is air-cooled to room temperature after holding.

4. The device according to claim 2, characterized in that: In step e, during casting, the resin sand mold is preheated to a temperature of 150-200°C.

5. The device according to claim 2, characterized in that In step e, before casting, the ladle used to hold the molten steel is heated and baked by a ladle baking device.

6. The device according to claim 5, characterized in that: The bun baking equipment comprises a bracket, a rotating arm, an upper cover plate, a roll-up device and a bun baking mechanism; The bracket is fixedly arranged, the rotating arm is rotatably and swingably installed on the bracket, the upper cover is installed on the rotating and swinging end of the rotating arm, and the bun baking mechanism is installed on the upper cover, which includes a combustion unit and an auxiliary combustion unit.

7. The device according to claim 6, characterized in that: The combustion unit includes a gas pipe, a gas valve, a flame nozzle and a metal hose; The gas pipe is connected to an external gas supply device, a gas valve is arranged on the gas pipe to control the switching amplitude of the gas pipe, a flame nozzle is installed at the center of the upper cover plate, and the flame nozzle is connected to the gas pipe through a metal hose.

8. The device according to claim 7, characterized in that: The flame spray head is provided with a cone that is adjustable for lifting and lowering and spoiler rods that are arranged in a circular shape and staggered along the inner diameter of the flame spray head.

9. The device according to claim 8, characterized in that: The auxiliary combustion unit includes an auxiliary air pipe, a butterfly valve, a fan and a flexible connecting pipe; The auxiliary air pipe is connected to an external air supply device, a butterfly valve is installed on the auxiliary air pipe to control the opening and closing amplitude of the auxiliary air pipe, and the auxiliary air pipe is connected to the flame nozzle through a hose, and the connection part is located above the cone and the spoiler rod.

10. The device according to claim 9, characterized in that: The upper cover plate is also equipped with an argon blowing mechanism, which includes an air inlet pipe, a telescopic pipe and a telescopic rod; The air intake pipe is connected to an external air supply device, and the other end of the air intake pipe is connected to an air distribution area set inside the upper cover plate. The telescopic pipe is set below the upper cover plate, connected to the air distribution area, and the telescopic pipe is driven by a telescopic rod installed on the upper cover plate to be telescopic.

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